No sound alerts for text messages

[scubacat]

Hello! I've been having issues for more than a year where I don't get any sound alerts for incoming SMS messages when my screen is locked. They appear on my lock screen, but the screen doesn't light up or sound when the message comes in. The only way I know I have a message is if I pick my phone up to turn the screen on and I see it on the lock screen. I had an iPhone 8 and upgraded to a 12 Pro last year and have had the issue on both phones. It's causing serious issues because I'm missing time-sensitive messages from work that have to be answered within 5 minutes, and I can't keep picking up my phone every 5 minutes to see if there's a message coming in. iMessage works just fine, it's only SMS messages that cause the problem, and only when the screen is locked (the sound alert goes through if my phone is unlocked and I'm using it). Any solutions?

 

[now i see it]

If the 12 was restored from your 8 backup, maybe the bug/corruption got transferred from the 8 to the 12?
I don’t know if that’s possible, but the likelihood that both your phones are experiencing the same rare problem is suspicious.
Really the only way to rule it out is set up a phone as new and see if that fixed it. Yes it’s a royal time wasting pain.